The 861 AKA VT-19 and 38161 is a 400 watt tetrode with maximum ratings to 20 MHz. This tube was first available in 1929. They were used in WWII with shipboard transmitters and even in submarines in spite of their size. The first example is an RCA marked 38161 and the second with a black cap is marked 861. The third example was made by Westinghouse and has a spiral grid and not a screen mesh as in the RCA tubes.
Length = 17.22" Diameter = 6.62"
Max voltage = 3500
Max current = 300 ma
Fil voltage = 11
Fil current = 10 amps